The 'ensembles' identified by the InterLink working group on Software Intensive Systems 
comprise vast numbers of components adapting and interacting in complex and even unforeseen
ways. If the analysis of ensembles is difficult, their synthesis, or engineering, is downright
intimidating. We show, following a recent three-level approach to agent-oriented software 
engineering, that it is possible to specialise that intimidating task to three levels of 
abstraction (the 'micro', 'macro' and 'meso' levels), each potentially manageable by interesting 
extensions of standard formal software engineering. The result provides challenges for formal 
software engineering but opportunities for ensemble engineering.